The present invention relates to a method for the feeding of a material web provided with transverse crease lines with the help of a rotating driver which engages with the crease lines by means of edges arranged around its circumference.
The present invention relates also to an arrangement for the feed of a material web provided with transverse crease lines by means of a rotating driver which has axial edges distributed around its circumference adapted to engage with the crease lines.
Packages of a variety of different types are often manufactured from a semi-rigid plastic, paper or cardboard material which is supplied to an automatic machine and, while being fed stepwise through the machine is successively converted into a finished package. In the manufacture of packing containers e.g. for liquid foodstuffs, such as milk and the like, the machine is supplied with a weblike, laminated material. The material is relatively rigid, but flexible, and comprises a central carrier layer of paper which is coated at least on one side with a homogeneous plastic layer. To facilitate the folding of the material necessary for the conversion to finished packing containers, the material web is provided with a regularly recurring pattern of weakened or crease lines, along which the folding of the material will afterwards take place. The feed of the material occurs intermittently or continuously, but at varying speed according to a predetermined cycle in rhythm with the conversion of the web to individual packing containers. It is a prerequisite for the processing of the material web and conversion of the the same into individual packing containers that the material web must always be fed to an exactly predetermined position wherein the processing or the shaping is carried out, since otherwise the folding of the material will not take place along the crease lines mentioned earlier. An accurately defined length of feed which guides the material to a correct position is important also for other reasons, e.g. in the cases when the material is to be provided with opening arrangements or with a printed pattern which has to be placed so that it will be in correct position on the finished packing container.
The feed of a material web provided with crease lines, patterns or other irregularities in the aforementioned manner is called feed in register, and occurs very often in package manufacture. The most common method for ensuring a sufficiently accurate keeping in register is to provide the material web with a repeated pattern of photocell marks, e.g. printed dots or lines of contrasting colour, which pattern is in an accurately defined relation to the crease line pattern, print pattern or the like of the material web. With the help of photocells co-operating with the said photocell marks the feed, which may take place with the help of driver elements in the form of rollers, feed jaws or the like, is then monitored and continuously corrected so that a good synchronous feed is achieved and maintained. Such a correcting system also has the advantage that any inaccuracies in the crease line pattern, that is to say small deviations from the specified nominal dimension between transverse crease lines following upon each other exercize no negative effect. However, the system is complicated in its setup, and consequently also contains possible sources of error. It is a further disadvantage that the accuracy of the synchronization will depend directly on the accuracy with which the photocell marks are applied to the material web (in relation to the crease line pattern).
It is an object of the present invention to overcome the aforementioned disadvantages and to provide a method for the feeding of a material web provided with transverse crease lines in register, which method is simple and uncomplicated and renders unnecessary special marks on the material web made for keeping in register.
It is a further object of the present invention to provide a method of feed which automatically ensures that the feed takes place in register independently of the faults which may exist in the distance between transverse crease lines of the material web.
These and other objects have been achieved in accordance with the invention in that a method of the type described in the introduction has been given the characteristic that the linear distance between two crease lines intended for engagement with the driver is reduced through temporary bending of the material web situated between, so that each of the crease lines engages with its edge.
Preferred embodiments of the method in accordance with the invention have been given moreover the characteristics which are evident from subsidiary claims 2 and 3.
It is also an object of the present invention to provide an arrangement for the feed of a material web provided with transverse crease lines in register which arrangement is not affected by the previous disadvantages.
It is a further object of the present invention to provide a feed arrangement which is simple and uncomplicated and which by direct mechanical engagement with the transverse crease lines of the material web fed ensures that the feed is taking place in register with the crease line pattern, independently of the deviations which occur in the nominal distance between consecutive transverse crease lines.